Method of fabricating a motorhome

ABSTRACT

A method of fabricating a motorhome, wherein the motorhome comprises a chassis, a vehicle frame, and a coach body. In one embodiment, the method begins by prefabricating the frame by joining a plurality of parallel elongate members with cross-tie members. The frame is prefabricated separate from the chassis, and in one embodiment, the frame is prefabricated upside down such that the underside of the frame is accessible for attachment of a plurality of bulkheads. Then, the frame is rotated upright and positioned atop the chassis. In one embodiment, the rails of the chassis lie inside a channel defined by the plurality of bulkheads. Next, additional bulkheads are joined to the frame and chassis to further interconnect the frame and chassis. Preferably, the additional bulkheads comprise an opening such that the additional bulkheads can surround the chassis on all sides. Finally, the coach body is assembled on the frame.

RELATED APPLICATIONS

[0001] This application is a divisional of U.S. application Ser. No.09/965,463 filed Sep. 26, 2001, which is a continuation-in-part of U.S.application Ser. No. 09/728,946 filed Dec. 1, 2000 (issued on Apr. 1,2003 as U.S. Pat. No. 6,540,285), and claims the benefit of U.S.Provisional Application No. 60/318,136 filed Sep. 7, 2001.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to the field of recreationalvehicle fabrication and, in particular, to methods of prefabricating amotorhome frame and then joining the frame to a prefabricated vehiclechassis to provide a motorhome with increased structural strength andinterior ceiling height with improved production efficiency and reducedcost and time of production.

[0004] 2. Description of the Related Art

[0005] Motorhomes have become an increasingly popular and common meansof recreation. Motorhomes are self-propelled vehicles that include aliving space inside. Motorhomes typically provide sleeping areas,cooking facilities, and self-contained water supplies and toiletfacilities. More elaborate motorhomes can include refrigerator/freezerunits, showers and/or bathtubs, air conditioning, heaters, built ingenerators and/or power inverters, televisions, VCRs, and clotheswashers and dryers. Motorhomes provide many of the amenities of aresidential home while on the road away from home and are popular forthis reason. Motorhome users will typically use the motorhome to travelto a recreational area and live in the motorhome for some period oftime. It is not unusual for people, particularly retired persons, to usea motorhome as their primary residence. Motorhome users often havefamilies with children and, as their trips are often of a recreationalnature, will often invite friends or family along on the trip.

[0006] It can be understood that since a motorhome will often be used bya large number of people and often for an extended period of time, themotorhome manufacturers and customers will seek as many amenities and asmuch interior living space as possible. A major goal of motorhomemanufacturers and their customers is to maximize the amount of usableliving space inside their motorhomes. However, the overall size of anmotorhome is limited both by vehicle code regulations and by practicallimitations on what is reasonable to drive and maneuver. Vehicle codesrestrict the maximum height, width, and length of vehicles that may bedriven on public roads. Also, as a vehicle increases in size, it becomesincreasingly difficult to drive and can become physically too large topass through locations that the driver may wish to go. In addition, asthe motorhome gets physically larger, more fuel is required to move it,which increases the cost of operation. Accordingly, many motorhomes areprovided with slide-out room structures which are extendable so as toincrease the motorhome's footprint and interior living space once thevehicle comes to rest.

[0007] An additional design constraint on the construction and design ofmotorhomes is their overall weight. Since an motorhome is intended to bemobile, an integral power plant is provided and the engine anddrive-train have an upper design limit on the weight it is capable ofmoving. In addition, the chassis, suspension, wheels, and brakes of amotorhome also have upper design limits as to how much weight they cansafely accommodate. These weight limits are established after carefulengineering analysis and the weight ratings are endorsed and enforced byresponsible governmental agencies. Exceeding the established weightlimits of a power-train or chassis component can lead to excessive wearand failure, unacceptable performance, and exposure to liability in caseof an accident. It is also highly desirable that as much payload aspossible is available to accommodate passengers and cargo, i.e.available weight load between the wet weight of the motorhome and thetotal maximum gross weight of the motorhome.

[0008] A particular issue with the weight of a motorhome is itsdistribution along a vertical axis. The distance of the vehicle's centerof mass from the road surface has a dramatic effect on the handlingcharacteristics of the vehicle. The closer the center of mass is to theroad surface, the shorter the moment arm between the center of mass andthe roll axis of the vehicle. The shorter the moment arm between thecenter of mass and the roll axis of the vehicle, the less tendency thevehicle will have to lean in turns. Leaning in turns is uncomfortablefor the occupants and typically places uneven loads on the tires andsuspensions, compromising turning ability. Motorhomes, typically beingquite tall, often exhibit significant leaning in turns. However, withinthe height available in a motorhome, the weight should be concentratedas low as possible. For this reason, heavy items, such as generators,storage and holding tanks for water and fuel, and the engine areoptimally placed low in the chassis.

[0009] Since motorhomes are mobile structures, they are typicallyexposed to the stresses of driving over roads that are in places quiterough. In addition, an motorhome will often have to travel over somedistance of dirt surface to reach a camping space. Since an motorhome istypically used outdoors, it is exposed to the stresses of inclementweather and high winds. It can be appreciated that structural integrityis highly desired in an motorhome. However, the weight and sizelimitations previously mentioned place a limit on the strength of anmotorhome. Accordingly, motorhomes are constructed to be as strong, butas light as possible.

[0010] The chassis of a motorhome is typically constructed on a steelladder frame chassis. The chassis is a partially complete vehicle and isgenerally procured from a manufacturer such as Freightliner or FordMotor Company. The chassis typically consists of two parallel framerails extending the length of the chassis and interconnected withseveral perpendicular cross-braces to form a ladder frame. An engine,transmission, and fuel tank(s) are generally placed between the framerails near one end. Suspension, steering, brake, and road wheelassemblies are attached outboard of the frame rails.

[0011] The coach bodywork, which provides and encloses the living spaceof the motorhome, is typically made from a laminate that can includelight gauge sheet metal, plywood, vinyl, and insulation. The laminate isbuilt to be strong, lightweight, weather resistant, and durable. Thecoach bodywork may also include a supporting framework. The floor of thecoach typically rests indirectly on the chassis frame and the verticalwalls extend upwards from the floor. The roof of the coach rests on anddepends on the vertical walls of the body for structural support.

[0012] A completed motorhome may be up to 45′ long and 13′ 6″ high inmost states. The chassis is generally on the order of 1′ high and iselevated some distance above the ground by the suspension and wheels toprovide ground clearance for suspension movement and clearing obstaclesin the road. The interior flooring in current art motorhomes istypically elevated a significant amount above the upper face of thechassis in order to facilitate installing ancillary equipment. Inaddition, many prior art motorhomes route cooling or heating air ductsadjacent the roof structure or mount air-conditioning units on the roof.Under the overall height limit previously mentioned, these structures inor on the roof intrude into the available interior height envelope andlimit the usable interior vertical space. Current motorhomes typicallyoffer interior ceiling heights of 6′ 9″ or less. The slide-outs incurrent art motorhomes do not typically provide sufficient room insidefor adults to stand upright. As the slide-out area is a living space inthe extended position, it can be appreciated that to be forced to stoopor crouch inside the slide-out is an inconvenience for the users of suchmotorhomes.

[0013] An additional difficulty arises with motorhomes of theconstruction described above when the vehicle drives over rough terrain.Motorhomes are essentially rectangular and are thus susceptible totwisting deflection as opposed to a triangulated structure such as atrailer or a fifth wheel. Motorhomes of the construction described aboveare not particularly strong under torsional forces such as arise whenone comer of the vehicle drops or rises compared to the others, forexample when a wheel drops into a pothole or rut or the vehicle drivesover a curb or speed bump at an angle. Such maneuvers “cross-up” therectangular frame and impose twisting forces. These forces, exerted overthe relatively large dimensions of a typical motorhome, can causesignificant displacement in the coach. This can cause cracks to appearin the coach, jam door and window openings, dislodge interior fitments,and generally cause wear and tear on the vehicle.

[0014] Furthermore, as stated, a motorhome is typically constructed onan unfinished vehicle chassis procured from a separate manufacturer,such as Freightliner or Ford Motor Company. As such, the motorhomemanufacturer is dependent on delivery of the preassembled chassis beforemotorhome fabrication can begin. This results in a series productionthat has increased assembly time as compared to a parallel process.expensive to purchase and inventory.

[0015] From the foregoing, it can be appreciated that there is acontinuing need for a stronger motorhome coach construction that alsoprovides increased interior living space. The structure should minimizeweight to the motorhome and should also maintain as low a center ofgravity as possible to benefit vehicle handling characteristics. Thereis also a need for a method of fabricating the motorhome with increasedefficiency and reduced cost and construction time.

SUMMARY OF THE INVENTION

[0016] The aforementioned needs are satisfied by the invention which, inone aspect, is a method of manufacturing a motorhome comprising thesteps of assembling a three-dimensional space frame wherein the spaceframe defines a generally planar floor area, interconnecting the spaceframe with an unfinished vehicle chassis, and attaching living structureto the interconnected space frame and vehicle chassis so as to define aninterior living area. In one aspect, assembling the three-dimensionalspace frame comprises assembling a planar ladder frame and attachingplanar bulkheads to the ladder frame and in certain aspectsinterconnecting the space frame with the vehicle chassis comprisesattaching the ladder frame to the vehicle chassis along first horizontalregions of the vehicle chassis and attaching the bulkheads along secondvertical regions of the vehicle chassis.

[0017] Further aspects of the invention include installing a heating,ventilation, and air conditioning (HVAC) system such that the majorityof the weight of the HVAC system is positioned below the floor areaand/or installing the HVAC system such that the heating andair-conditioning portions of the HVAC system share a common air return.

[0018] Other aspects of the invention include installing the HVAC systemsuch that the furnace and air-conditioning portions of the HVAC systemare positioned outside the living area. Certain aspects of the inventioninclude assembling the living structure such that an outside roofstructure has a convex exterior contour and attaching an extensibleslide-out structure to the interconnected space frame and vehiclechassis wherein the slide-out is constructed such that an adult ofabove-average height can stand upright inside the slide-out. Inparticular aspects of the invention, the frame is assembled in anupside-down orientation and inverted to a right-side-up orientationprior to attachment to the unfinished vehicle chassis.

[0019] The invention is also a method of lowering the center of mass ofa motorhome comprising the steps of assembling a planar ladder framewherein the ladder frame defines a floor plane, attaching planarstructural members to the ladder frame such that, in an assembledconfiguration, the planar structural members extend downwards from theladder frame, and attaching the space frame to an unfinished vehiclealong an attachment plane such that the floor plane is adjacent theattachment plane less the thickness of the ladder frame and so as tocreate a three-dimensional space frame wherein the space frame extendsbelow the floor plane. Certain of these aspects further compriseinstalling a heating, ventilation, and air conditioning (HVAC) systemsuch that the majority of the weight of the HVAC system is positionedbelow the floor plane. The invention can include installing the HVACsystem such that the heating and air-conditioning portions of the HVACsystem share a common air return and the aspect wherein the planarstructural members form storage areas positioned below the attachmentplane.

[0020] Yet another aspect of the invention is a method of increasingproduction efficiency of motorhome manufacture, the method comprisingassembling a motorhome frame separately from an unfinished vehiclechassis, attaching the frame to the unfinished vehicle chassis so as todefine an interconnected space frame among the frame and unfinishedvehicle chassis, and constructing a motorhome coach on theinterconnected frame and vehicle chassis. These aspects can includeinstalling a heating, ventilation, and air-conditioning (HVAC) systemwherein the HVAC system has a common air return. Yet other aspects ofthe invention include assembling the motorhome frame separately from theunfinished vehicle chassis and attaching the frame to the unfinishedvehicle chassis so as to define the interconnected space frame betweenthe frame and unfinished vehicle chassis comprising attaching bulkheadsto the frame and the vehicle chassis such that the bulkheads arestructural components of the space frame and form storage areas. Theseand other objects and advantages will become more fully apparent fromthe following description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is an isometric view of a preassembled vehicle framemounted on a preassembled chassis forming the framework for a motorhomewith a high interior ceiling including an HVAC system with common airreturn;

[0022]FIG. 2 is an exploded, isometric view of a partially assembledvehicle frame and a preassembled chassis;

[0023]FIG. 3 is a perspective view of a partially complete preassembledframe;

[0024]FIG. 4 is a perspective view of the frame of FIG. 3 with aplurality of bulkheads attached forming a three dimensional space frame;

[0025]FIG. 5 is an end section view of a motorhome including the vehicleframe and a slide-out;

[0026]FIG. 6 is a perspective view of a completed motorhome; and

[0027]FIG. 7 is a top view of one embodiment of an interior build-out ina motorhome.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0028] Reference will now be made to the drawings wherein like numeralsrefer to like parts throughout. FIG. 1 shows an preassembled vehicleframe 100 mounted to a preassembled chassis 102. The vehicle frame 100,mounted to the chassis 102 in the manner that will be described ingreater detail below, facilitates the construction of a motorhome 104(FIGS. 5 and 6) with a greater interior ceiling height, which in thisembodiment, is at least 7′-6″ in a reduced time span. The vehicle frame100 also facilitates, in a manner described below, building a slide-out122 (FIGS. 5 and 7) with a greater interior height. The vehicle frame100 also facilitates mounting of relatively massive items, such asgenerators, furnaces, storage and holding tanks, and the like low to theground so as to provide a lower center of mass for the motorhome 104.

[0029] The vehicle frame 100 provides a strong three dimensional spaceframe 118 inhibit twisting of the vehicle frame 100 under torsionalforces such as would arise when the motorhome 104 drives over uneventerrain so as to lift or drop a wheel 116 with respect to the otherwheels 116. The vehicle frame 100 further defines integral storage areas106 as part of the structure of the vehicle frame 100 in a manner thatwill be described in greater detail below. The vehicle frame 100 furtherfacilitates routing of a heating, ventilation, and air conditioning(HVAC) system 110 below the beltline of the frame 100 so as to avoidintrusion of the HVAC system 110 into the interior living space of themotorhome 104 to further enable increased interior ceiling height of themotorhome 104 employing the vehicle frame 100. The HVAC system 110comprises a furnace 164 and air conditioning unit 162 includingevaporator, condenser, and compressor. These relatively heavy portionsof the HVAC system 110 are installed below the beltline of the frame 100thereby maintaining a lower c.g. than other designs.

[0030] As can be advantageously seen in FIG. 2, the chassis 102 of thisembodiment, is a split rail or raised rail chassis 102 of a type knownin the art. The chassis 102 of this embodiment is a diesel pusher typeand is available commercially from Freightliner, LLC. of Portland, Oreg.as Model XC. The chassis 102 comprises a pair of raised rails 112 andtwo pairs of lower rails 114. The raised rails 112 and lower rails 114are rigid elongate members formed of c-channel steel approximately 2¾″by 9″ and approximately ¼″ thick. The raised rails 112 and the lowerrails 114 are all substantially parallel. A first and second end of eachcenter rail 112 overlies a lower rail 114 over a length of approximately402″ in one embodiment and is attached along the overlying extent to thelower rail 114 in a known manner. Each pair of interconnected raisedrails 112 and attached lower rails 114 are displaced a lateral distanceof approximately 34″ and are further interconnected by a plurality oforthogonally extending cross-beams (not illustrated) rigidly attached soas to form a ladder frame structure of a type well known in the art. Theupper surfaces of the raised rails 112 defines a generally horizontallydisposed attachment plane for attachment of the frame 100 to the chassis102 in a manner that will be described in greater detail below. Therails 112, 114 also present vertically arranged surfaces for furtherattachment of the frame 100 to the chassis 102.

[0031] The chassis 102 also comprises a plurality of road wheels 116with corresponding suspension, brake systems, steering, and drivemechanisms of types known in the art that are positioned atsubstantially the front and rear comers of the chassis 102 in the mannerillustrated in FIG. 2. The road wheels 116 enable the motorhome 104 toroll along the road and to be steered and braked in a well understoodmanner. The road wheels 116 are positioned adjacent the overlappingraised rails 112 and lower rails 114. The chassis 102 further comprisesan engine assembly, transmission, drive axle, fuel system, andelectrical system (not illustrated) of types known in the art to providethe motive power for the motorhome 104. These items are advantageouslylocated substantially within the plane of the rails 112 to lower thecenter of mass of the chassis 102 and thus the motorhome 104.

[0032] The chassis 102 of this embodiment is highly resistant to bendingalong longitudinal and transverse axes. However, the chassis 102, byitself, is susceptible to twisting along the plane of the longitudinaland transverse axes due to torsional forces. Such torsional force mayarise when a road wheel(s) 116 at one comer of the chassis 102 isdisplaced either above or below the plane of the remaining road wheels116. Additionally, the torque of the engine exerts a torsional force onthe chassis 102.

[0033] The motorhome 104 of this embodiment is assembled on and aroundthe interconnected vehicle frame 100 and the chassis 102. The motorhome104 provides users with a vehicle having a variety of living spaces andamenities fitted within the motorhome 104. The partitioning of theinterior living spaces and placement of interior amenities can bereadily implemented by one of ordinary skill in the art. One embodimentof interior partitioning and furnishing of the motorhome 104 isillustrated in FIG. 6. The construction and features of the motorhome104 will be described in greater detail below.

[0034] As is illustrated in FIGS. 1, 2, 3, and 4, the vehicle frame 100comprises a floor section 101 which is formed from a plurality ofL-channel elongate members 174, C-channel elongate members 176, andsquare tubing elongate members 180. The L-channel elongate members 174of this embodiment are approximately 1½″ wide, 6⅜″ tall, and 34′ longand are made of sheet steel approximately 0.0897″ thick. The C-channelelongate members 176 of this embodiment are approximately 1½″ wide, 3½″tall, and 34′ long and are made of sheet steel approximately 0.0897″thick. The square channel elongate members 180 of this embodiment areapproximately 2″ square in cross section, approximately 97″ long, andare made of sheet steel with a wall thickness of approximately ⅛″. Itshould be appreciated that the configurations of the elongate members174, 176, 180 herein described are simply one embodiment and that otherconfigurations of the elongate members 174, 176, 180 could be employedby one of skill in the art without detracting from the spirit of thepresent invention.

[0035] The L-channel elongate members 174 and the C-channel elongatemembers 176 extend substantially the length of the vehicle frame 100.The C-channel elongate members 176 define a cavity 182 and the L-channelelongate members 174 define an inside comer 184 as illustrated in FIGS.3, 4, and 5, Detail B. The square channel elongate members 180 arefixedly attached via welding in a known manner to the L-channel elongatemembers 174 such that a first and second end of each square channelelongate member 180 is flush with the inside comer 184 of an L-channelelongate member 174 such that the two L-channel elongate members 174 areparallel, the plurality of square channel elongate members 180 extendperpendicular to each of the L-channel elongate members 174, and theplurality of square channel elongate members 180 are thus allrespectively parallel.

[0036] As can be seen in FIG. 3, a C-channel elongate member 176 isfixedly attached via welding in a known manner to each L-channelelongate member 174 such that the C-channel elongate member 176 abuts afirst or second end of the square channel elongate members 180 andfurther such that the cavity 182 of the C-channel elongate member 176 isadjacent the L-channel elongate member 174. Thus, the L-channel elongatemembers 174 enclose the cavities 182 and thus create closed structures.The abutment of the C-channel elongate members 176 against the squarechannel elongate members 180 inhibits displacement and bending of thesquare channel elongate members 180 with respect to the L-channel 174and C-channel 176 elongate members. The interconnection of the L-channel174 and C-channel 176 elongate members also defines two shelves 186extending the length of the L-channel 174 and C-channel 176 elongatemembers. The interconnected L-channel 174, C-channel 176, and squarechannel 180 elongate members thus define a preassembled rigid ladderframe 100 structure that is highly resistant to bending and flexing.

[0037] In one embodiment, a plurality of Z-channel elongate members 190extend longitudinally and are positioned so as to be parallel to,aligned with, and between the rails 112.

[0038] The abutment of the C-channel elongate members 176 against thesquare channel elongate members 180 increases the stiffness of the jointbetween the square channel elongate members 180 and the L-channelelongate member 174. This is because loads, which would be otherwisecarried solely by the joint between the square channel elongate members180 and the L-channel elongate members 174, can now be distributedthrough the C-channel elongate members 176. The interconnected L-channel174, C-channel 176, and square channel 180 elongate members thus definea rigid ladder frame structure that is highly resistant to flexure. Bymaking the frame 100 more rigid, the overall motorhome 104 willsubsequently be more stiff to thereby enhance the performance of themotorhome 104. The upper surface of the frame 100 defines a floor planeto which additional structure of the motorhome 104 is attached asdescribed below. Areas of the lower surface of the frame 100 areattached along the attachment plane of the chassis 102 in a manner thatwill be described in greater detail below.

[0039] As shown in FIG. 3, the elongate members 174, 176, 180, 190 arejoined to form the vehicle frame 100 such that the frame 100 isassembled upside down. The frame 100 is assembled in an upside downorientation to facilitate attachment of other elements as will bedescribed in greater detail below with reference to FIG. 4. The elongatemembers 174, 176, 180, 190 are held in position during attachment by ajig in a known manner. Thus, the frame 100 can be assembled without achassis 102 present.

[0040] The vehicle frame 100 also comprises a plurality of transverselyextending bulkheads 120 illustrated in FIGS. 1, 2, and 4. In oneembodiment, the bulkheads 120 are rigid, planar pieces of steelapproximately 0.0897″ thick. The bulkheads 120 are rectangular,triangular, or compound rectangular in shape as can be seen in FIGS. 2and 4. Approximately 2″ of the outer edges of the bulkheads 120 arefolded via known sheet metal forming techniques so as to extendgenerally perpendicular to the major plane of the bulkheads 120 therebyforming attachments areas 121 and also so as to increase the stiffnessof the bulkheads 120. The bulkheads 120 are attached to the frame 100 soas to extend generally perpendicular to the major plane of the frame 100in the next step in the fabrication process, illustrated in FIG. 4. Asthe frame 100 is upside down, the bulkheads 120 can rest on the frame100 during attachment rather than needing to be held up if the frame 100were in its final right side up orientation. A particular advantage ofthe frame 100 of this embodiment, is that the frame 100 defines athree-dimensional space frame 118 prior to attachment of the frame 100to the chassis 102. Thus, the frame 100 is highly resistant to bendingand twisting forces even if not attached to the chassis 102.

[0041] Following attachment of the bulkheads 120, the frame 100, asshown in FIG. 4, is then inverted and placed on the chassis 102 asillustrated in FIG. 1. The frame 100 is attached to the chassis 102along the attachment plane, in this embodiment, at the points ofintersection of the transversely extending elongate members 180 and thelongitudinally extending rails 112. The bulkheads 120 of the frame 100are also fixedly attached to the vertical sides of the rails 112, 114 ofthe chassis 102 to further interconnect the chassis 102 and the vehicleframe 100. The bulkheads 120 are attached to the vehicle frame 100 andthe chassis 102 so as to extend downward from the vehicle frame 100 andthe chassis 102. The rigid interconnection of the bulkheads 120 with thechassis 102 and the vehicle frame 100 boxes in the rails 112, 114 of thechassis 102 further defining a three-dimensional space frame structure118 adjacent the chassis 102. The rigidly interconnected vehicle frame100 and chassis 102, boxed in by the bulkheads 120, are much moreresistant to twisting forces than the chassis 102 by itself. Inaddition, the floor plane of the frame 100 is advantageously positionedimmediately adjacent the upper surface of the chassis 102 less thethickness of the ladder portion of the frame 100. This maximizes theavailable vertical extent of the motorhome 104 available for interiorliving space within a set total exterior height.

[0042] As stated above, the motorhome 104 manufacturer ordinarily ordersthe incomplete vehicle chassis 102 from another manufacturer, likeFreightliner. The chassis 102 is a significant fraction of the overallmaterial cost of the motorhome 104. With the fabrication methoddescribed above, the frame 100 can be prefabricated to completion beforethe chassis 102 is obtained. More specifically, a major portion of theassembly of the motorhome 104 can be completed before the chassis 102 isreceived, and then the comparatively quick task of joining the completedframe 100 to the chassis 102 can be achieved once the chassis 102 isreceived. This aspect of the invention facilitates a just-in-timemanufacturing capability thereby reducing the time capital is tied up inthe chassis 102 prior to completion of the motorhome 104. This aspect ofthe invention results in cost savings for the manufacturer of themotorhome that can be passed on as price reductions to the consumerand/or increase the manufacturer's profit margin.

[0043] The motorhome 104 also comprises a front loop 192 as shown inFIG. 1. The loop 192 is a generally rectangular structure attached atthe front of the motorhome 104 to the frame 100. The loop 192 providesstructural support for interior body assemblies in the driver's andfront passenger's area as well as the front exterior bodywork of themotorhome 104 and the front windshield. The loop 192 is assembled from aplurality of elongate steel members via welding in a similar manner tothat previously described with respect to the frame 100.

[0044] The motorhome 104 of this embodiment comprises a slide-out 122(FIGS. 5 and 7). The slide-out 122 is a movable structure containedwithin the motorhome 104 that is extensible between a retracted, travelposition and an extended, live-in position. The slide-out 122 is agenerally rectangular structure closed on the top and bottom and threesides and open on the remaining fourth side. The slide-out 122 of thisparticular embodiment is approximately 3½′ deep, 13′-4″ long, and of6′-1″ interior height. The slide-out 122, in the extended, live-inposition, provides additional interior living space to the users of themotorhome 104.

[0045] In particular, the slide-out 122 provides an additional 45½square feet of living space when the slide-out 122 is extended. Aparticular advantage of the slide-out 122 of this embodiment is that theinterior ceiling height is approximately 6′ 141 as referred above. Thisenables a person of above average height to stand up within theslide-out 122. This greatly increases the convenience and livability ofmotorhomes 104 employing the vehicle frame 100 which enables theslide-out 122 as herein described. As will be described in greaterdetail herein below, the increased living space in the main section ofthe motorhome 104 and in the slide-out 122 is due, in part, to theconfiguration of the vehicle frame 100.

[0046] The slide-out 122 includes a slide-out mechanism 124. Theslide-out mechanism 124, of this particular embodiment, is anelectromechanical assembly of a type known in the art. The slide-outmechanism 124 extends and retracts the slide-out 122 between theretracted, travel position and the extended, live-in position inresponse to user commands. The slide-out mechanism 124 also physicallysupports the slide-out 122 in transition between the travel and live-inpositions. The slide-out mechanism 124 may comprise other mechanismssuch as manual, pneumatic, or hydraulic without departing from thespirit of the present invention. However, the electromechanicalmechanism of the preferred embodiment of the present invention affordsadvantages over other means. In particular, the slide-out mechanism 124of this embodiment offers greater user friendliness than knownmechanisms for extending slide-out rooms which are manually actuated.Furthermore, the slide-out mechanism 124 of this embodiment is lighterand requires less maintenance than known pneumatic or hydraulicslide-out extension mechanisms.

[0047] The slide-out 122 and slide-out mechanism 124 are attached to thevehicle frame 100. The vehicle frame 100, when interconnected with thechassis 102 and the bulkheads 120 as previously described, is highlyresistant to bending and twisting. Thus, the slide-out 122 and slide-outmechanism 124, attached to the rigid structure of the vehicle frame 100has a low susceptibility to jamming or sticking due to flexing of themotorhome 104 as it is driven about. The slide-out 122 is also able tosupport a significant amount of weight, such as furniture and occupants.It should be appreciated that alternative embodiments of the inventioninclude additional slide-outs 122.

[0048] The vehicle frame 100 also comprises seat supports 126. The seatsupports 26 are, in one embodiment, rectangular structures formed fromsheet steel approximately ⅛″ thick and are approximately 12{fraction(13/16)}″ by 22½″. The seat supports 126 are fixedly attached to thevehicle frame 100 via a plurality of bolts and/or welding in a knownmanner adjacent the front end of the vehicle frame 100. The seatsupports 126 provide a support and attachment structure for passengerseats 128 of known types. The passenger seats 128 provide seatingaccommodations for driver and passengers in a known manner.

[0049] The vehicle frame 100 of this embodiment, also comprises twostorage area floors 130. The storage area floors 130 are rigid compositerectangular members approximately 3¼″ thick, 95″ wide, and 98″ long and3¼″ thick, 65″ wide, and 44″ long. The storage area floors 130 are acomposite of tube steel, foam, and Luan vacuum bonded together. Thestorage area floors 130 are fixedly attached along the attachment areas121 along lower edges of the bulkheads 120 with welds and/or bolts in aknown manner. The storage area floors 130, together with the bulkheads120, define storage areas 106. The storage areas 106 of this embodimentextend substantially the full width of the motorhome 104. The storageareas 106 of this embodiment are two rectangular spaces approximately95″ by 98″ by 25½″ and 65″ by 42″ by 25½″. The storage areas 106 of thisembodiment are approximately 8″-9″ higher than comparable storage areaswould be in an embodiment employing a straight rail design chassis. Inparticular, the raised rails 112 of the chassis 102 are 8″-9″ higherthan the lower rails 114 and thus provide 8″-9″ additional height to thestorage areas 106.

[0050] The storage area floor 130, comprising a rigid member fixedlyattached along the length of the lower edges of the bulkheads 120,further defines the three-dimensional structural space frame 118. Thestructural space frame 118, comprising a plurality of rigid panels andrigid elongate members fixedly interconnected along their adjoiningedges and arranged at right angles to each other, forms a structurallyrigid space structure. It will be appreciated that distorting the spaceframe 118 would require separation of the joints between componentmembers and/or bending of the rigid members. This further increases thetorsional rigidity of the interconnected vehicle frame 100, chassis 102,bulkheads 120, and storage area floor 130 assembly.

[0051] The vehicle frame 100 also comprises a plurality of storage areadoors 132 (FIG. 5). In one embodiment, the storage area doors 132 arerectangular, rigid structures approximately 2⅜″ thick by 25½″ by 8′long. The storage area doors 132 are a vacuum bonded composite offiberglass, Luan plywood, block foam insulation, and aluminum. Thestorage area doors 132 enclose the storage areas 106. The storage areadoors 132 have an insulation value of R11 and thus provide thermalinsulation to the interior of the storage areas 106. The storage areadoors 132 also retain objects placed in the storage areas 106 fromfalling out as the motorhome 104 moves about or from unintentionalremoval by curious children or thieves. The storage area doors 132 alsoinhibit intrusion of pests and windblown dirt, dust, and rain into theinterior of the storage areas 106 thereby befouling the interior andpossibly damaging items stored therein.

[0052] The storage area doors 132 are hingedly attached along either atop edge or a vertical edge of the storage area doors 132 to the vehicleframe 100. The storage area doors 132 can be raised to an elevatedposition to facilitate placing items into or removing items from theinterior of the storage areas 106. The storage area doors 132 arefurther positionable in a closed position to seal the interior of thestorage areas 106. The storage area doors 132, in a preferredembodiment, further comprise weather seals 133 and a latching mechanism135. The weather seals 133 are resilient, tubular structures of a typeknown in the art that are attached with adhesive to the periphery of thestorage area doors 132 on the side of the storage area doors 132 facingthe motorhome 104. The weather seals 133 improve the seal between thestorage area doors 132 and the storage areas 106 in a known manner. Thelatching mechanism 135 is a lock mechanism of a type well known in theart which lockably secures the storage area doors 132 in the closedposition to further inhibit unintentional opening of the storage areadoors 132.

[0053] The motorhome 104 also comprises a coach floor 134. The coachfloor 134 of this embodiment is formed from a plurality of rectangularpieces of ¾″ tongue and groove plywood, placed so as to abut each otherin a coplanar fashion. The coach floor 134 is a planar, rectangularstructure approximately 97¼″ by 420⅝″. The coach floor 134 is placeddirectly on the floor section 101 of the vehicle frame 100 so as to reston the shelves 186. The coach floor 134 is attached to the floor section101 of the vehicle frame 100 via a plurality of screws and adhesive in aknown manner. The coach floor 134 provides a continuous flooring surfacefor the motorhome 104 to support occupants and furniture in the interiorof the motorhome 104. The coach floor 134 also provides a support andattachment surface for padding, carpeting, tile, linoleum, or otherinterior floor finishings.

[0054] As is illustrated in FIGS. 1, 2, and 5, the floor section 101 ofthe vehicle frame 100 is mounted such that the bottom surface of thefloor section 101 is positioned directly on the rails 112. As such, thecoach floor 134 is elevated above the rails 112 of the chassis 102 by adistance substantially equal to the thickness of the members comprisingthe floor section 101. This results in the upper surface of the coachfloor 134 being flush with driver platform from front to back. Thesubstantially planar floor section 101 yields a better bond between thefloor section 101 and the chassis 102.

[0055] Moreover, the floor section 101 is attached to the upper surfaceof the raised rails 112 and is also connected to the sides and thebottom side of the raised rails 112 and the lower rails 114 via thebulkheads 120 that are also connected to the floor section 101. As isillustrated in FIGS. 1 and 2, the floor section 101 is attached to theraised rails 112 and the lower rails 114 at periodic intervals along thelength of the floor section 101 of the vehicle frame 100. Byinterconnecting the floor section 101 to the raised rails 112 and thelower rails 114 using the space frame 118 that encloses the raised rails112 and the lower rails 114 along the top and sides, twisting of theframe 100 when the wheels 116 of the motorhome 104 are verticallydisplaced from each other is reduced.

[0056] The motorhome 104 also comprises coach walls 136. The coachwalls, in one embodiment, 136 are generally planar, rectangularstructures approximately 2⅜″ thick, 90″ tall, and 416⅞″ long. The coachwalls 136 are made from a laminated composite of fiberglass, phenolicLuan plywood, foam insulation, and interior decor panel which are vacuumbonded together with an aluminum frame. The coach walls 136 providephysical structure to the motorhome 104. The coach walls 136 alsoinsulate the interior of the motorhome 104 against heat transfer andsound. The coach walls 136, of this embodiment, are approximately ½″thicker than walls typically used in the art and have a higherinsulation rating than other known walls. The insulation rating of thecoach walls 136 of this embodiment is R11. The coach walls 136 alsocomprise various openings to accommodate windows, doors, slide-outs 122,vents, etc. the formation and placement of which are readily realized byone skilled in the art.

[0057] The motorhome 104 also comprises a coach roof 140. The coach roof140, in one embodiment, is a planar, rectangular structure approximately97¼″ wide by 371″ long. The coach roof 140 is formed from a laminate ofa rubber outer roofing layer, Luan plywood, ultra-light high-densityblock foam insulation core, and a one-piece carpeted inner ceiling layerbonded with an extruded aluminum welded superstructure 138.

[0058] The coach roof 140 is substantially planar along a lower face 142and convexly contoured along an upper face 144. The coach roof 140 isapproximately 5½″ thick at the thickest region near the center of thecoach roof 140 and convexly tapers off to the sides and towards thefront and back to a thickness of approximately 2½″ along the edges ofthe coach roof 140. Thus, the upper face 144 of the coach roof 140 has acrowned contour. The crowned contour of the upper face 144 of the coachroof 140 inhibits pooling of water and accumulation of snow and debrison the coach roof 140. Thus, the motorhome 104, fitted with the coachroof 140 as herein described, can more readily shed water, snow, anddebris and minimize the deleterious effects of retaining water or debrisin contact with the materials of the coach roof 140. The crowned contourof the upper face 144 also improves the structural durability of thecoach roof 140 because avoiding accumulation of water and snow willminimize the vertical weight loads of heavy snow or water which couldpotentially otherwise bow the coach roof 140 leading to distortion,cracking, or separation of joints. The crowned contour of the coach roof140 also improves the aesthetics of the motorhome 104 because morereadily shedding debris helps to minimize adhesion of dirt and thusmaintains a cleaner appearance to the exterior of the motorhome 104.

[0059] The motorhome 104 also comprises a plurality of attachmentassemblies 146. The attachment assemblies 146 are extruded from aluminumalloy in a known manner. The attachment assemblies 146 are elongatemembers that extend substantially the length of the motorhome 104. Theattachment assemblies 146 interconnect the coach walls 136, a storagearea skirt frames 132 a, the coach roof 140, and the vehicle frame 100in a manner that will be described in greater detail below.

[0060] As viewed in a perpendicular cross-section (as shown in FIG. 5)the attachment assemblies 146 comprise a planar attachment area 150, ahollow rounded, closed rectangular channel 152 region, and an innerpartition 154. It should be appreciated that the attachment assemblies146 are unitized, extruded assemblies and the planar attachment area150, the rectangular channel 152, and the inner partition 154 hereindescribed are regions of the attachment assemblies 146 and arematerially and structurally continuous with each other.

[0061] The attachment area 150 is a rectangular, planar region of theattachment assemblies 146 that is long as the length of the coach andextends vertically from the rectangular channel 152 approximately 2⅛″and provides a convenient structure for attaching the attachmentassemblies 146. The rectangular channel 152 is a closed, structuralelement of the attachment assemblies 146 approximately 2″ by ¾″ andincreases the stiffness of the attachment assemblies 146 to bending andtwisting according to well understood structural principles. The innerpartition 154 extends vertically approximately ⅝″ within the rectangularchannel 152 and spans and internally partitions the rectangular channel152 and further stiffens the attachment assemblies 146. The innerpartition 154 is substantially coplanar with the attachment area 150.

[0062] The attachment assemblies 146 are fixedly attached to an upperand lower edge of the coach walls 136 such that the rectangular channels152 are positioned between outer layers of the coach walls 136 as shownin FIG. 3, details A and B. The attachment assemblies 146 are furtherattached to the coach walls 136 such that the rectangular channels 152are positioned flush with upper and lower edges of the coach walls 136.The attachment areas 150 of the attachment assemblies 146 thus extendbeyond the edges of the coach walls 136 approximately 2⅛″. Theattachment assemblies 146 are attached to the coach walls 136 with anadhesive, such as MA425 from Plexus of Danvers, Mass. in a known manner.

[0063] The coach walls 136 with the attachment assemblies 146 attachedare placed on the coach floor 134 such that the attachment area 150 isadjacent the edge of the coach floor 134 and the rectangular channel 152rests on the coach floor 134. This placement of the coach walls 136 andattached attachment assemblies 146 results in the edge of the coachfloor 134 occupying the corner defined between the attachment area 150and the rectangular channel 152. This placement further results in thecoach walls 136 straddling the coach floor 134 such that approximatelyhalf of the thickness of the coach walls 136 is overlying the coachfloor 134. This enables the coach walls 136 to partially rest on thecoach floor 134 for additional vertical load support while stillmaintaining clearance for recessed attachment of the coach walls 136such that the attachment devices do not protrude beyond the outer faceof the coach walls 136.

[0064] The attachment assemblies 146 in one embodiment are attached tothe coach floor 134 and the vehicle frame 100 via a plurality of screws156 positioned approximately every 5″ along the length of the attachmentassemblies 146. The screws 156 of this embodiment are 10-16×1″ of a typeknown in the art and installed in a known manner.

[0065] The coach roof 140 is positioned on the coach walls 136 such thatthe attachment areas 150 are adjacent the edges of the coach roof 140and such that the coach roof 140 partially overlies the coach walls 136.The attachment areas 150 are attached to the coach roof 140 via aplurality of screws 156 placed approximately every 5″ along the lengthof the edges of the coach roof 140.

[0066] The motorhome 104 also comprises a plurality of trim pieces 160.The trim pieces 160 are elongate members of semi-rigid material, such asvinyl, approximately 20′ long, 5″ wide and {fraction (1/16)}″ thick. Thetrim pieces 160 are arc-shaped in cross section and are attached to thealuminum superstructure 138 via a friction fit achieved in a knownmanner. The trim pieces 160 are positioned to abut each other so as toextend the full length of the coach roof 140. The outer rubber roofinglayer of the coach roof 140 overlies the trim pieces 160.

[0067] The trim pieces 160 cover the screws 156 attaching the coach roof140 to the coach walls 136. The trim piece 160 obscures the view of thescrews 156 to thereby improve the aesthetics of the motorhome 104. Thetrim piece 160 also shields the screws 156 and the upper edges of thecoach walls 136 from rain, snow, and debris. Thus the trim piece 160inhibits accumulation of water and debris adjacent the screws 156 andthe upper edges of the coach walls 136 so as to inhibit corrosion andfouling of the screws 156 and the coach walls 136. The trim piece 160also inhibits intrusion of water and debris into the interior of thecoach walls 136 which could compromise the strength and structuralintegrity of the coach walls 136.

[0068] The HVAC system 110 in this embodiment comprises the airconditioning unit 162, the furnace 164, a manifold 166, a duct 170, atleast one register 172, an intake 171, and a filter 173 as illustratedin FIG. 1. The intake 171 (shown in section view in FIG. 1) commonlydirects air from the interior of the motorhome 104 to the airconditioning unit 162 and the furnace 164. The filter 173 is positionedwithin the intake 171 and filters the air entering the HVAC system 110.The air conditioning unit 162 receives air from the interior of themotorhome 104 via the intake and cools this filtered incoming air anddirects the cool air into the interior of the motorhome 104. The furnace164 warms incoming air and directs the warm air into the interior of themotorhome 104. The manifold 166 receives air from both the airconditioning unit 162 and the furnace 164 and routes the air to the duct170. The duct 170 extends substantially the length of the interior ofthe motorhome 104. The duct 170 carries the warm or cool air to at leastone register 172. The registers 172 direct cool or warm air, receivedfrom the duct 170, into the interior of the motorhome 104. The registers172 includes a screen to inhibit objects falling into the interior ofthe registers 172 and the duct 170.

[0069] The common intake 171 is advantageously formed on two sides bywood paneling that serves both to direct the air inside the intake 171and also provide interior trim in the interior of the motorhome 104. Inaddition, by directing air to both the air-conditioning unit 166 and thefurnace 164, the common intake 171 of this embodiment, obviates the needfor the separate air intakes for the A/C unit and the furnace of otherdesigns. The common intake 171 of this embodiment also facilitates theuse of a single filter 173 for the HVAC system 110. This single filter173 reduces the time and expense of maintaining the HVAC system 110 bythe end user as compared to other designs with multiple filters for theseparate A/C and furnace systems. This commonality reduces the time andexpense of construction of the HVAC system 110 as well as reducing theweight thereof.

[0070] The HVAC system 110, of this embodiment, is located within orbelow the plane of the chassis 102. Positioning the air conditioningunit 162 and the furnace 164, which are both relatively heavy items,within or below the plane of the chassis 102 further lowers the centerof mass of the motorhome 104 to thereby improve the road handling of themotorhome 104. The placement of the HVAC system 110 of this embodimentalso distances the duct 170 and registers 172 from the coach roof 140.Other known motorhome designs rout HVAC ducting adjacent the roof of thevehicle which exposes the cool air to thermal heating from sunlightincident on the roof of the vehicle. In the motorhome 104 of thisembodiment, the duct 170, register 172, and air conditioning unit 162are shaded from incident sunlight by the motorhome 104. Thus, the HVACsystem 110 can more efficiently provide cool air to the interior of themotorhome 104. This improves the occupant's comfort in hot weather andreduces fuel costs for powering the HVAC system 110.

[0071] A further advantage of the HVAC system 110 of this embodiment isthat the air conditioning unit 162, duct 170, and register 172 whichcarry cool air are located below the living space of the motorhome 104.As is well understood by those of ordinary skill in the art, a coolerthan ambient surface, such as the air conditioning unit 162, duct 170,and register 172 induces liquid water to condense out of the atmosphereif the temperature of the surface is at or below the dew point. When airconditioning ducting is routed above the living space of a motorhome,liquid water that condenses on the ducting is drawn downwards bygravity. This can induce liquid water to intrude into walls, ceilings,and other interior materials. It can be appreciated that liquid watercan readily damage the structural integrity of typical motorhomebuilding materials. Liquid water can also stain and warp interiormaterials, damaging the aesthetics of a motorhome. The air conditioningunit 162, duct 170, and registers 172 of this embodiment are positionedbelow the living space of the motorhome 104 and thus water thatcondenses out during use of the HVAC system 110 is drawn downwards andaway from the motorhome 104 without intruding into the living spaces ofthe motorhome 104.

[0072] An additional advantage of the HVAC system 110 of this embodimentis that placement of the HVAC system 110 adjacent and below the beltlineof the chassis 102 obviates the need to place portions of an HVAC systemon the roof of the motorhome 104. Other known HVAC systems placeportions of the system on the exterior roof of a motorhome. Thisrequires that the major plane of the outer roof be lowered with respectto the roof of the present invention so as to maintain the overallheight restrictions previously mentioned. Lowering the exterior roofheight results in corresponding lowering of the interior ceiling heightand a corresponding reduction in the interior space and livability ofsuch a motorhome.

[0073] Yet another advantage of the HVAC system 110 of this embodimentis that placement of the HVAC system 110 adjacent and below the beltlineof the chassis 102 distances the furnace 164 and air conditioning unit162 from the interior of the motorhome 104. The air conditioning unit162 and furnace 164 are relatively noisy in operation. Placing the HVACsystem 110 outside the interior of the motorhome 104 distances the noisesources of the air conditioning unit 162 and the furnace 164 and thusprovides a quieter, more comfortable living environment for users of themotorhome 104.

[0074] Although the preferred embodiments of the present invention haveshown, described and pointed out the fundamental novel features of theinvention as applied to those embodiments, it will be understood thatvarious omissions, substitutions and changes in the form of the detailof the device illustrated may be made by those skilled in the artwithout departing from the spirit of the present invention.Consequently, the scope of the invention should not be limited to theforegoing description but is to be defined by the appended claims.

What is claimed is:
 1. A method of lowering the center of mass of amotorhome comprising the steps of: assembling a planar ladder framewherein the ladder frame defines a floor plane; attaching planarstructural members to the ladder frame so as to define athree-dimensional space frame such that, in an assembled configuration,the planar structural members extend downwards from the ladder frame;attaching the space frame to an unfinished vehicle along an attachmentplane such that the floor plane is adjacent the attachment plane lessthe thickness of the ladder frame and so as to create athree-dimensional space frame wherein the space frame is extends belowthe floor plane.
 2. The method of claim 10, further comprisinginstalling a heating, ventilation, and air conditioning (HVAC) systemsuch that the majority of the weight of the HVAC system is positionedbelow the floor plane.
 3. The method of claim 11, comprising installingthe HVAC system such that a heating and an air-conditioning portion ofthe HVAC system share a common air return.
 4. The method of claim 10,wherein the planar structural members form storage areas positionedbelow the attachment plane.
 5. The method of claim 10, wherein the spaceframe is assembled in an upside-down orientation and inverted to aright-side-up orientation prior to attachment to the unfinished vehicle.6. A method of increasing production efficiency of motorhomemanufacture, the method comprising: assembling a motorhome frameseparately from an unfinished vehicle chassis; attaching the frame tothe unfinished vehicle chassis so as to define an interconnected spaceframe among the frame and unfinished vehicle chassis; constructing amotorhome coach on the interconnected frame and vehicle chassis.
 7. Themethod of claim 15, further comprising installing a heating,ventilation, and air-conditioning (HVAC) system wherein the HVAC systemhas a common air return.
 8. The method of claim 15, wherein assembling amotorhome frame separately from an unfinished vehicle chassis andattaching the frame to the unfinished vehicle chassis so as to definethe interconnected space frame between the frame and unfinished vehiclechassis comprising attaching bulkheads to the frame and the vehiclechassis such that the bulkheads are structural components of the spaceframe and form storage areas.
 9. The method of claim 15, wherein themotorhome frame is assembled in an upside-down orientation and invertedto a right-side-up orientation prior to attachment to the unfinishedvehicle chassis.